Modern silviculture often requires the planting of large numbers of genetically identical plants that have been selected to have advantageous properties. Production of new plants by sexual reproduction, which yields botanic seeds, is usually not feasible. Asexual propagation, via the culturing of somatic or zygotic embryos, has been shown for some species to yield large numbers of genetically identical embryos, each having the capacity to develop into a normal plant.
Somatic cloning is the process of creating genetically identical plants from plant somatic tissue. Plant somatic tissue is plant tissue other than the male and female gametes. In one approach to somatic cloning, plant somatic tissue is cultured in an initiation medium which includes hormones, such as auxins and/or cytokinins that initiate formation of embryogenic cells that are capable of developing into somatic embryos. The embryogenic cells are then further cultured in a maintenance medium that promotes multiplication of the embryogenic cells to form pre-cotyledonary embryos (i.e., embryos that do not possess cotyledons). The multiplied embryogenic cells are then cultured in a development medium that promotes development of cotyledonary somatic embryos.
At the end of development phase, the embryos may be present in a number of stages of maturity and development, and are typically attached to or imbedded in embryogenic suspensor mass (ESM). Separation and singulation are processing steps that typically occur at the end of development and maturation in which plant embryos are physically separated from each other and the underlying ESM before further processing, such as placement onto germination or pre-germination medium for further treatment prior to insertion into manufactured seeds.